First things first, I wouldn't rely on organic traffoc to a review blog for affiliate commission for your sole income, things come and go, so ideally you would need to build quite a few sites or a substantial business for it to be stable.

However, to your question, An incredibly niched down site may have its advantages, but the winner above all will be the review site with the most useful information that has all the comparisons and information that searchers want.

Just buying a focused domain and thinking type-in traffic from google will come, will not work any longer unless you can do it at scale. So if your passion really lies behind reviewing kitchen appliances (right!) I would build a site that is different than others and fills a gap in that area so it will be something that actually ranks and gets traffic... and in turn some amount of revenues.